Electric valve translating circuit



May 14, 1935. I B. A. CASE 2,001,567

ELECTRIC VALVE TRANSLATING CIRCUIT Filed Dec. 22, 193:5

Inventor: Byron A. Case,

i tcohney.

Patented May 14, 1935 UNITED STATES PATENT OFFICE Byron A. Case, Fort Wayne, Ind, assignor to General Electric Company, a corporation of New York Application December 22, 1933, Serial No. 703,565

3 Claims.

My invention relates to electric valve translating circuits and more particularly to such circuits utilizing valves of the thermionic cathode roe.

Electric discharge devices, or valves, of the thermionic cathode type, either directly or indirectly heated, have come to be used extensively in many electric translating circuits {or the control, transmission, or conversion of electrical energy. In many or these circuits, the life of the electric valve becomes an important consideration. It has been found that the life at such electric valves may be materially lengthened if their thermionic cnhodesare operated at a substantially constant which is last auilcient to provide adequate electron tor the ordinary operating oondittma a! the device. However, itiswellknowathatan inmionic catlwdeelectrondisehargedevtceisei iootiveto increase the ottbe cathodamdthialstrue'wheoherthecnthodeisof the directly or the indirectly heated type, althoughthe phenomermwhichgiveristothia increase in temperamre are diflerent in the two cases.

It is an object of my invention therefore to provide an improved electric valve translating circuit, including an electric valve of the thermionic cathode type. in which the tenmeratine oi the cathode of the valve will be maintained substantially constant irrespective of the operatingconditimso! thesyscemotwhichitis a part.

ltisanotherobjectoi'mytoprovide an improved electric trting system including an electric valve of the thermionic cathodetypeinwhichtheene of the thermionic cathode is decreased in accordance widimcreasesinthelnadom'mntotthesystom.

In accordancewith one embodiment of my invention, the thermionic cathode of an electric discharge device included in an electric translating circuit is energized from a source of a1- ternating current through a saturable reactor. The reactor is provided with a saturating winding which is constantly energized with a. unidirectional current, as for example, by means of an auxiliary rectifying device operating from the source of alternating current. The saturable reactor is also provided with an auxiliary saturating winding which operates differentially with respect to the first saturating winding and is energized in accordance with the load current transmitted by the system. with such an arrangement, an increase in load on the system tends to desaturate the reactor and thus increase its impedance, which, in turn, is effective to decrease the energization oi the thermionic cathode of the electric valve. This decrease in the energization of the thermionic cathode with increases in load current of the system tends to compensate for the heating effect of the increased load current of the system and thus maintain the temperature of the cathode sub stantially constant.

For a better understanding of my invention, together with other and further objects thereof, retencnce is had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. The single figure of the drawing is a schematic representation of my invention as applied to the control oi the cathode heating of an electric discharge valve rectifier.

Referring now more particularly to the drawing, there is illustrated an electric valve translating system for transmitting energy from a single phase alternating current supply circuit in to a direct current load circuit ii. This system includes a transformer I2 having a primary windmg connected to the system H and a secondary winding provided with an electrical midpoint connected to one side oi the circuit Ii and with end terminals connected to the other side of the circuit ii through electric valves i3 and i4 connected in a conventional manner to secure full wave rectification. The electric valves l3 and H are each provided with an anode and a thermionic cathode which may be of either the indirectly heated type, as illustrated, or the directly heated type. Electric valves l3 and i4 may also be provided with control electrodes, in case it is desired to control the energy transmitted in the system. In this case, the control electrodes are connected to the common cathode circuit through current limiting resistors IS, a bias battery 18 and the secondary winding of a control transformer ll. The primary winding of the transformer Il may be energized from the alternating current circuit l0 through any suitable phase shifting arrangement such as an impedance phase shifting circuit comprising a midtapped inductive winding It, a reactor I9, and a variable resistor 20, the primary winding of the transformer ll being connected between the midpoint of the winding I8 and the junction between the reactor l9 and resistor in a well known manner. If desired, a smoothing reactor 2| may be ill included in the direct current circuit of the system.

The heaters of the thermionic cathodes of the electric valves l3 and M ar connected to be energized from the circuit it through a transformer 22, in series with the primary winding of which is connected a saturaole reactor 23. The reactor 23 is provided with a saturating winding 24 connected to be energized from any suitable source of unidirectional current substantially constant in magnitude, as for example, from a contact rectifier bridge 25 energized from the circuit it. If desired, a current adjusting resistor 26 and filtering capacitor 2'1 may be included in the energizing circuit of the saturating winding 24, and in some cases it may be desirable to include a ballast lamp 213, such as an iron. wire filament in a hydrogen atmosphere, or some other well known constant current device, to compensate for the effect of variations in the supply volt age on the saturation or" the reactor The reactor 22 is also provided with a saturating winding 29, which acts differentially with respect to the saturating winding i and is connected in series with the unidirectional current circuit i l of the system.

The general principles of operation of the above described rectifying apparatus per se is well understood by those skilled in the art, and need not be explained in detail. Electric valves i3 and i4 conduct alternately and the average energization oi the load circuit it may be controlled by varying the resistor 28 which is effective to vary the phase or the alternating potentials impressed upon the control electrodes of the valves l3 and I4 and thus to vary the portions of the cycles of alternating potential during which these valves are conductive, as is well understood by those skilled in the art.

As stated above, variations in the load current of the system, as efiected by the above described operation or by variations in the connected load on the system, are effective to vary the temperature of the cathodes of the electric valves [3 and I4, increases in load current tending to increase the temperature of the cathodes. The above described circuit, however, compensates for this tendency of the cathode to increase in temperature with increase in load current. For example, consider the operation of the system under a very light load when the energization of the saturating winding 29 in series with the load circuit l l is very small. Under these conditions, t -e energization of the saturating winding 24 through the rectifier bridge 25 is effective to saturate substantially the reactor 23 and reduce its reactance to a minimum, thus energizing the transformer 22 to a maximum and heating the cathodes of the electric valves [3 and M. to a proper operating temperature to secure adequate electron emission for ordinary operating conditions of the system. In case the load current of the system increases, the energization of the saturating winding 29 will similarly increase, which, acting differentially with respect to the saturating winding 24 tends to desaturate the reactor 23 and to increase its impedance. Obviously, an increase in the impedance of the reactor 23 is effective to decrease the energization of the transformer 22, and the cathode heaters of the electric valves l3 and M, to compensate for the effect of the increased load current on the cathode temperatures. In this manner the temperature of the cathodes of the electric valves l3 and [4 may be maintained substantially constant or may be made to increase only very slightly with increases in load current on the system, in accordance with the requirements of the particular apparatus. Obviously, adjusting the resistance 26 in series with the main saturating winding 24 will vary the temperature regulation characteristics of the cathodes of the electric valves I3 and H8, and, as stated above, the ballast lamp 28 will tend to maintain the energization of the saturating winding 24 substantially constant irrespective of variations of the supply voltage.

While I have described what I at present consider the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention, and I therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric translating system including a source, of alternating current and an electric valve provided with a thermionic cathode, a circuit for energizing said cathode from said source including a saturable reactor, means for normally constantly saturating said reactor, and means responsive to an electrical condition of said system for modifying the saturation of said reactor to regulate the heating of said cathode.

2. An electric translating system including a source of alternating current and an electric valve provided with a thermionic cathode, a circuit for energizing said cathode from said source including a saturable reactor, a constantly energized saturating winding for said reactor, and means responsive to the load current of the system for saturating said reactor differentially with respect to said saturating winding.

3. An electric translating system including a. source of alternating current and an electric valve provided with a thermionic cathode, a circuit for energizing said cathode from said source including a reactor provided with a saturating winding, rectifier means connected to substantially constantly energize said saturating winding from said source, and an auxiliary saturating winding for said reactor connected to act differentially with respect to said first mentioned winding and energized in accordance with the load current of the system.

BYRON A. CASE. 

